By MICHAEL J. DE LA MERCED

Published: April 5, 2011

8:48 p.m. | Updated

On the evening of July 24, 2008, Danielle Chiesi, a hedge fund executive, called Raj Rajaratnam, the chief of the Galleon Group hedge fund, and told him some potentially interesting news she had gleaned about Akamai Technologies.

''They're going to guide down,'' she told Mr. Rajaratnam, according to a recording of their conversation played in the United States District Court in Lower Manhattan on Monday, referring to Akamai's plans to lower its earnings guidance.

''I just got a call from my guy. I played him like a finely tuned piano.''

Shortly afterward, according to federal prosecutors, Mr. Rajaratnam added to his bet against the company's stock.

In another secretly recorded phone conversation on July 30, minutes after Akamai lowered its earnings guidance, Mr. Rajaratnam called Ms. Chiesi again.

''Hi Dani, I just wanted to say thank you,'' he said, according to another recording.

Though she was not physically present, Ms. Chiesi took center stage in the courtroom for much of the testimony and evidence on Monday afternoon. For the first time, jurors heard the voice of one of the central figures in the government's investigation.

Azam Ahmed and Guilbert Gates/The New York Times Click on the above graphic to get a visual overview of the Galleon information network.

Prosecutors played a half-dozen recordings aimed at bolstering their case that Mr. Rajaratnam, who is accused of making $45 million in illegal trades, was connected to a broad insider trading conspiracy. She was a participant in every conversation

In January, Ms. Chiesi pleaded guilty to three counts of participating in an insider-trading conspiracy.

The recordings played on Monday also suggested a cozy rapport between Ms. Chiesi and Mr. Rajaratnam. During the July 24 call, she repeatedly asked the hedge fund manager to let her bet against Akamai's stock by a little bit every day until the earnings announcement the next week.

The next week, the two appeared to celebrate over their trading profits.

''It's a conquest for me,'' Ms. Chiesi said during the July 30 call. ''It's mentally fabulous for me.''

At one point, Ms. Chiesi and Mr. Rajaratnam appeared to be concerned that others would divine a pattern in their trading.

In a phone call on Aug. 27, 2008, he counseled her to show a pattern of repeatedly buying and selling shares of Advanced Micro Devices.

As far back as February 2008, Ms. Chiesi was determined to get more information about Akamai, regularly calling up the company's executives to elicit information, J. D. Sherman, Akamai's chief financial officer, testified.

Prosecutors also sought to show a quid-pro-quo relationship between Ms. Chiesi and a midlevel Akamai executive, Kieran Taylor.

In the two recordings of their often flirtatious conversations, Ms. Chiesi offers her Akamai contact information, including advice on buying shares in A.M.D.

She also suggests that she can get Mr. Taylor, then a senior director of marketing, a better job, owing to her high-powered connections, including one with a high-level I.B.M. executive, Robert W. Moffat Jr.

Mr. Taylor appeared ready to reciprocate with confidential information he gleaned from his job. During a phone call on Oct. 10, 2008, he told Ms. Chiesi, ''I have a major present for you.''

Ms. Chiesi: ''Drugs?''

Mr. Taylor: ''No, no, no.''

Ms. Chiesi: ''I hope not.''

Mr. Taylor: ''Information, information.''

Mr. Taylor has not been charged in the case.

Earlier Monday, prosecutors also sought to link Mr. Rajaratnam to improper trading in Google. JoAnn Horne, a senior partner at the marketing firm Market Street Partners, testified that Shammara Hussain, a former hedge fund analyst hired as a junior employee, was privy to advance notice that Google would miss analysts' estimates for its second quarter that year.

For both Akamai and Google, Mr. Rajaratnam's lawyers sought to show that their client's trades were prompted by his own research and publicly available information like research reports.

For Akamai in particular, John Dowd, a lawyer for Mr. Rajaratnam, demonstrated that Akamai's stock had actually fallen nearly 20 percent during most of June and July, even before the company lowered its earnings guidance. Research reports highlighted Akamai's troubles as its clients cut back on spending and competitors like Level 3 and AT&T added pressure.

On Monday, prosecutors and defense lawyers also battled over whether a decade-old video could be shown of Roomy Khan, who prosecutors say was another link in the Galleon insider trading network, faxing confidential Intel information to Mr. Rajaratnam. The government is seeking to connect the video to later communications between Mr. Khan and Mr. Rajaratnam, one of which suggested, ''Don't buy Polycom until I give guidance.''

The judge overseeing the case, Richard J. Holwell, has not yet decided whether the video can be shown.

Prosecutors said that they might be prepared to rest their case on Wednesday.

Mr. Rajaratnam's lawyers said that they would likely begin their case on Monday.

This is a more complete version of the story than the one that appeared in print.

PHOTO: Raj Rajaratnam, center, of the Galleon Group, entered Federal District Court on Monday with his lawyer, John Dowd, right. (PHOTOGRAPH BY MARK LENNIHAN/ASSOCIATED PRESS)